Limnology and Oceanography, September 2016, Vol.61(5), pp.1826-1838
Surface waters contribute substantially to carbon dioxide (CO) emissions to the atmosphere. However, global estimates remain uncertain due to methodological difficulties, such as in precisely estimating gas transfer in steep upland streams. Here, we addressed the question of what drives CO evasion from steep mountainous stream network of the European Alps by assessing the spatial and temporal variation of partial pressure of CO (CO) for 148 streams and the gas transfer coefficient for CO () for 88 locations within this 254 km watershed. Results show that log can be predicted reasonably well ( = 0.71, 〈0.001, = 88) using a statistical model based on slope, average width, flow velocity and stream discharge. Also, most sites were supersaturated in CO with significant variation in CO due to season (September vs. December) and time of day (day vs. night), but not stream order. Resulting median CO evasion rates were 145, 119, 46, 43, and 50 mg C m h at 1 to 5 order streams, respectively. CO evasion was dependent on season and time of day, with the highest evasion (184.0 kg C h) during growing season at nighttime, followed by 124.6 kg C h during daytime. Dormant season nighttime evasion was 30.9 kg C h and daytime evasion only 17.1 kg C h. Overall we conclude that CO evasion of steep mountainous streams depends on seasonal and diurnal variation in CO and reach‐specific variability in . These controls strongly alter landscape‐scale CO evasion estimates, with implications for regional to global carbon budgets.
Atmospheric Carbon Dioxide – Environmental Aspects ; Diurnal Cycles (Earth Sciences) – Observations;